HangtownMatt
Bronze Member
Can a person tell, just by looking, if the wheels have been adjusted to the widest postition? Or, do you need to remove the wheels? Tires from rims?
HangtownMatt
HangtownMatt
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R1 vs R4 and tractor width
- Thread starter woodlandfarms
- Start date
- Views: 7058
HangtownMatt said:Can a person tell, just by looking, if the wheels have been adjusted to the widest postition? Or, do you need to remove the wheels? Tires from rims?
HangtownMatt
YEs, by looking at the owners manual. This is true with my NH TN70A
Bob
weesa20
Silver Member
I think another consideration needs to include available traction. Many accidents happen because tires begin to spin and then the tractor begins to slide either backwards (downhill) or downhill sideways in an unexpected direction. Either way, once the tire or tires regain traction, it is a precarious position to be in. Imagine a tractor with turf tires traversing a sidehill and then sliding 10 feet down the hill and then regaining traction. The momentum can tip the tractor. Now imagine that the tractor had R1s that never lost traction...there are many variables that need to be considered when determining tractor safety.
In a situation where either tire would lose traction, then the COG comes into play.
W
In a situation where either tire would lose traction, then the COG comes into play.
W
weesa20 said:I think another consideration needs to include available traction. Many accidents happen because tires begin to spin and then the tractor begins to slide either backwards (downhill) or downhill sideways in an unexpected direction. Either way, once the tire or tires regain traction, it is a precarious position to be in. Imagine a tractor with turf tires traversing a sidehill and then sliding 10 feet down the hill and then regaining traction. The momentum can tip the tractor. Now imagine that the tractor had R1s that never lost traction...there are many variables that need to be considered when determining tractor safety.
You have described dynamic rollover, something we all know by instinct is an entirely different problem than staic rollover (what we talk about most often). Both scare the cripes out of me, but dynamic rollover really scares me the most.
Bob
HangtownMatt
Bronze Member
Doc_Bob said:YEs, by looking at the owners manual. This is true with my NH TN70A
Bob
I'm not able to find this information in the Owner's Manual for my Mahindra 2615 HST.
Hangtownmatt
patrick_g
Elite Member
john_bud, I was with you until you said, "To tip the tractor over, you have to move the up-hill tire up higher than the CG of the tractor ." I do not believe this is true.
Ignoring the differences between static and dynamic stability for now lets start with the simple case, static. If the CG of the tractor-implement combination (carried implements not towed) is moved such that it is outside of the outermost support then the tractor will at least fall onto its side if not roll over. This is irrespective of the relationship of the high side wheel to the CG.
Example: Fill the FEL bucket full of heavy material and raise it as high as it will go. This raises the CG quite a bit. A small sideways tilt such as driving at right angles to the slope of the land can place the altered CG beyond the support and initiate an accident where the tractor lays down on its side. This greatly reduced angle of roll requirement prior to passing the point where the tractor will remain upright is one of the good reasons to be extremenly cautious about raising a heavy load very high while on a slope or when in motion.
Dynamic case: If you are in motion then centrifugal force is at work on your CG tending to roll you over to the outside of a curved path you may steer. The angle of tilt required to initiate a roll over is reduced the more G's you pull by turning. With a heavy load carried high you can easily roll over on level ground. Of course uneven ground with any lump in it can serve to launch you into a roll over event like special effects in a movie's chase scene.
Partially filled tires, up to about 50%, defininitely help lower the CG but at times the unbaffled free surface liquid fill might contribute a little to instability. I have cast iron wheel weights bolted to the rims instead of liquid fill and it is way better than not having any weight on the wheels, just not as extreme as filled tires but not so much bother or source of corrosion or...
Kubota forbids liquid fill in rear tires of my Grand L-4610HSTC, hence my use of wheel weights, which are approved.
Pat
Ignoring the differences between static and dynamic stability for now lets start with the simple case, static. If the CG of the tractor-implement combination (carried implements not towed) is moved such that it is outside of the outermost support then the tractor will at least fall onto its side if not roll over. This is irrespective of the relationship of the high side wheel to the CG.
Example: Fill the FEL bucket full of heavy material and raise it as high as it will go. This raises the CG quite a bit. A small sideways tilt such as driving at right angles to the slope of the land can place the altered CG beyond the support and initiate an accident where the tractor lays down on its side. This greatly reduced angle of roll requirement prior to passing the point where the tractor will remain upright is one of the good reasons to be extremenly cautious about raising a heavy load very high while on a slope or when in motion.
Dynamic case: If you are in motion then centrifugal force is at work on your CG tending to roll you over to the outside of a curved path you may steer. The angle of tilt required to initiate a roll over is reduced the more G's you pull by turning. With a heavy load carried high you can easily roll over on level ground. Of course uneven ground with any lump in it can serve to launch you into a roll over event like special effects in a movie's chase scene.
Partially filled tires, up to about 50%, defininitely help lower the CG but at times the unbaffled free surface liquid fill might contribute a little to instability. I have cast iron wheel weights bolted to the rims instead of liquid fill and it is way better than not having any weight on the wheels, just not as extreme as filled tires but not so much bother or source of corrosion or...
Kubota forbids liquid fill in rear tires of my Grand L-4610HSTC, hence my use of wheel weights, which are approved.
Pat
patrick_g said:Kubota forbids liquid fill in rear tires of my Grand L-4610HSTC, hence my use of wheel weights, which are approved.
Pat
Why no liquid?
Bob
patrick_g said:john_bud, I was with you until you said, "To tip the tractor over, you have to move the up-hill tire up higher than the CG of the tractor ." I do not believe this is true.
Ignoring the differences between static and dynamic stability for now lets start with the simple case, static. If the CG of the tractor-implement combination (carried implements not towed) is moved such that it is outside of the outermost support then the tractor will at least fall onto its side if not roll over. This is irrespective of the relationship of the high side wheel to the CG.
Example: Fill the FEL bucket full of heavy material and raise it as high as it will go. This raises the CG quite a bit. A small sideways tilt such as driving at right angles to the slope of the land can place the altered CG beyond the support and initiate an accident where the tractor lays down on its side. This greatly reduced angle of roll requirement prior to passing the point where the tractor will remain upright is one of the good reasons to be extremenly cautious about raising a heavy load very high while on a slope or when in motion.
Dynamic case: If you are in motion then centrifugal force is at work on your CG tending to roll you over to the outside of a curved path you may steer. The angle of tilt required to initiate a roll over is reduced the more G's you pull by turning. With a heavy load carried high you can easily roll over on level ground. Of course uneven ground with any lump in it can serve to launch you into a roll over event like special effects in a movie's chase scene.
Partially filled tires, up to about 50%, defininitely help lower the CG but at times the unbaffled free surface liquid fill might contribute a little to instability. I have cast iron wheel weights bolted to the rims instead of liquid fill and it is way better than not having any weight on the wheels, just not as extreme as filled tires but not so much bother or source of corrosion or...
Kubota forbids liquid fill in rear tires of my Grand L-4610HSTC, hence my use of wheel weights, which are approved.
Pat
Well, yeah. I was just talking about a tractor with 4 tires, no implements, no FEL, no backhoe. In order for the tractor to fall over (statically), it must be tilted quite a lot. Generalizing, that is when there is one tire higher than the CG of the tractor.
Try this, take a pic of your tractor from the rear and print it out on a full sheet. Put a pin in a spot at the middle of the rear differential to approximate the CG location, then tie a sting to the pin and hang it straight down. Now, rotate the picture of the tractor about the pin (CG location). Tell me, when the string gets to the outside edge of the low tire, where is the high tire in respect to the CG?
This is a simple static analysis. Dynamic analysis is much harder without using some math and a few sheets of paper. But, the point to remember is that when moving, the tractor is much less stable than when it is stationary. If you are on the verge of puckering standing still, it's a good bet you will be tight enough to crack walnuts if you're moving and hit a bump or a dip!
Oh yeah, if you drive your tractor around corners fast enough to pull "G's" (and I did note the plural!!), I want to watch you to cut the grass!! Must be more fun than NASCAR. Ye-ha.
And why the heck are you prohibited from filling the tires?? My old BH recommends filled tires and 1600# of rear wheel weights.
jb
patrick_g
Elite Member
DocBob, That was a very difficult question to get answered. I was probably one of the few people to ever read the whole manual and although my manual describes how to load the tires with calcium chloride giving the weight of different concentrations and the depression of the freezing point for the various concentrations, in one fell swoop they then mentioned that with a cab on the tractor you wre prohibited from filling the tires.
The dealer couldn't tell me (was unaware of the prohibition), other dealers couldn't tell me (also unaware and one even told me it was OK.) I faxed the page to the guy who told me it was OK and he got real quiet.
I had to talk to a few Kubota dudes to get an answer. I had thought that unbaffled free surface liquid splashing about in the partially filled tire might have been part of the concern but I never got high enough up in the Kubota food chain to get a definitive comment on that and not speaking Japanese I probably couldn't understand the answer.
Anyway the ROPS function of the cab meets the requirements for the tractor while carrying all recommended weights and implements within the prescribed limits set forth by the manufacturer but NOT with LOADED TIRES. Not sure if it is a mass, moment, free surface lquid, or just what sort of problem but apparently there is a failure mode with the cab model AND loaded tires in crash tests.
I have the max cast iron wheel weights that Kubota recommends (three sets on both sides) and usually have either a very HD brush hog (rated for 80HP) or a HD box blade (1300 lbs) on the 3PH unless I am specifically using a lighter implement such as a disk, middle buster, sub soiler, back blade, roto-tiller, cement mixer, PHD or whatever. With the FEL or pallet forks I have enough hydraulics to raise the rear wheels up off the ground with the heqaviest implements on the 3PH. I use that as a rule of thumb. If I can lift something with the buicket of forks and the rear wheels stay on the ground it is OK. Of course you have to manuver slow if the rears are too light and avoid slopes when really heavy in the front.
Note to JohnBud: Contained within "My Checquered Past" is my first paper chase which was in Physics and Math. I agree with your static analysis and the paper cutout approach to CG analysis is a clasic which every high school physics student should have been exposed to.
I have had my L-4610 in all 2 wheel AND 3 wheel combinations there are and most of them more than once. Sometimes the pucker factor was intense. I have 5 years and a bit over 700 hours on the clock with this Kubota and find that I have learned some things to not do again on purpose if they can be avoided.
Pat
The dealer couldn't tell me (was unaware of the prohibition), other dealers couldn't tell me (also unaware and one even told me it was OK.) I faxed the page to the guy who told me it was OK and he got real quiet.
I had to talk to a few Kubota dudes to get an answer. I had thought that unbaffled free surface liquid splashing about in the partially filled tire might have been part of the concern but I never got high enough up in the Kubota food chain to get a definitive comment on that and not speaking Japanese I probably couldn't understand the answer.
Anyway the ROPS function of the cab meets the requirements for the tractor while carrying all recommended weights and implements within the prescribed limits set forth by the manufacturer but NOT with LOADED TIRES. Not sure if it is a mass, moment, free surface lquid, or just what sort of problem but apparently there is a failure mode with the cab model AND loaded tires in crash tests.
I have the max cast iron wheel weights that Kubota recommends (three sets on both sides) and usually have either a very HD brush hog (rated for 80HP) or a HD box blade (1300 lbs) on the 3PH unless I am specifically using a lighter implement such as a disk, middle buster, sub soiler, back blade, roto-tiller, cement mixer, PHD or whatever. With the FEL or pallet forks I have enough hydraulics to raise the rear wheels up off the ground with the heqaviest implements on the 3PH. I use that as a rule of thumb. If I can lift something with the buicket of forks and the rear wheels stay on the ground it is OK. Of course you have to manuver slow if the rears are too light and avoid slopes when really heavy in the front.
Note to JohnBud: Contained within "My Checquered Past" is my first paper chase which was in Physics and Math. I agree with your static analysis and the paper cutout approach to CG analysis is a clasic which every high school physics student should have been exposed to.
I have had my L-4610 in all 2 wheel AND 3 wheel combinations there are and most of them more than once. Sometimes the pucker factor was intense. I have 5 years and a bit over 700 hours on the clock with this Kubota and find that I have learned some things to not do again on purpose if they can be avoided.
Pat
patrick_g said:I have had my L-4610 in all 2 wheel AND 3 wheel combinations there are and most of them more than once. Sometimes the pucker factor was intense. I have 5 years and a bit over 700 hours on the clock with this Kubota and find that I have learned some things to not do again on purpose if they can be avoided.
Pat
As they say, any landing you can walk away from...
On the loaded tires, the ROPS being the limiting factor makes sense. I think the actual ROPS is labled with the amount of weight it can protect you from. I'll have to take a look at it... Tractor, wheel weights, backhoe, loader (probably calculated with a full bucket) and cab all at once is probably more than the limit when you add CaCl2 loaded tires. That's actually the only reason that would make sense as to not filling the tires. Limiting liability.
jb
